1. Field of the Invention
The present invention relates to tray supply apparatuses and, more particularly, to a technique which is effective in use for supplying a plurality of trays each accommodating therein a plurality of articles such as electronic components, to an article withdrawal position.
2. Related Art Statement
Conventionally, there are known systems for supplying a plurality of trays each accommodating therein a plurality of articles such as electronic components, to an article withdrawal position. In almost all of the systems, the trays each accommodating the articles within partitioned or divided spaces in the form of a lattice are stacked upon each other. The articles are successively taken out from the uppermost tray. The trays, which are emptied, are successively discharged.
On the other hand, as another conventional system, there is also known a system in which a plurality of pallets accommmodated in a rack are optionally selected and are moved to an article withdrawal position.
In the former conventional systems, however, the trays cannot be discharged until the articles are all taken out. Further, naturally, it is impossible and meaningless to return the trays, from which the articles have once been discharged, to their respective original positions. Nevertheless, in the actual operation, there are many cases where it is necessary to optionally supply the articles which are of many kinds or types. In order to cope with this requirement or demand by the former conventional system, tray supply apparatuses corresponding in number to the kinds of the articles must be used in parallel relation to each other. Thus, not only the cost of equipment increases, but also a large amount of space is required. There may be a case where it is impossible to establish the tray supply apparatuses because of insufficient space.
Further, the later conventional system has been proposed to avoid drawbacks of the former conventional systems. In the latter conventional system, however, sudden or abrupt acceleration and deceleration, vibration, impact and the like are applied to the tray pallets at transportation thereof, whereby the article rebounds from each partitioned space in the tray within the tray pallet, or a shift or deviation in position of the articles occurs: Thus, automatic withdrawal operation of the articles are made impossible, drawbacks occur such as breakage due to collision, and the like. In order to eliminate such drawbacks, the following problems occur derivatively. That is, the construction is made complicated, and manufacturing is made troublesome or cumbersome, so that the cost increases.